Aflatoxins, a group of toxic mycotoxins, including Aflatoxin B1 (AFB1), Aflatoxin M1 (AFM1), Aflatoxin G1 (G1) etc., are produced by many species of Aspergilus. Aflatoxins are toxic and carcinogenic to animals and humans. Aflatoxins are widely present in grain, feed, and food, and the harmful effects to human beings are: (1) direct poisoning by consumption of untreated aflatoxins contaminated food; (2) poisoning by consumption of poultry, milk, etc. indirectly from untreated aflatoxins contaminated feed; (3) waste and disposal of crops or nuts contaminated with aflatoxins.
Because of these harmful effects, detoxification of aflatoxins has been studied for years. Some methods of transforming aflatoxins already exist, for instance: (1) Ammonization method: this method is used for wet feed. Because of the large amount of residual ammonia, it is banned in food processing by FDA. The application on feed is also limited. (2) NaOH method (for vegetable oil): due to high equipment investment, oil consumption, and cost, the method is no longer in use (3) White soil adsorption method: no longer in use because of higher labor cost, pollution etc. (4) Extraction method (for peanut powder, cotton seed, etc): it isn't widely used because of the high cost associated with extracting, recovering the solvent. (5) Heat method (268° C.): cost for heating and lose of flavor and nutrients make it less practical. (6) Biological method: bacteria or immobilized bacteria are used to resolve aflatoxins. Bacteria can destroy the nutrients of food; and the products and their toxicities are not well understood. Thus this application is limited to only a few types of feed and peanut oil. (7) Ultraviolet method: strong ultraviolet oxidation used to destroy aflatoxins is not consistent and high energy consuming. (8) Ultra-filtration method: it isn't practical due to high equipment cost and rigorous technical requirement. (9) Enzyme method: clone of liver cytochrome oxidase P450 in E. coli was used to transform aflatoxins (Brown D W, etc. Proc. Natl. Acad. Sc. USA. 1996).
To summarize, the chemical or physical methods to transform aflatoxins often require harsh conditions, but results in lower value for the treated grain, feed, and food. These methods are often not efficient and economical, thus difficult for large scale applications. P450 enzyme method does promote the metabolism of aflatoxins, but it may also lead to higher toxicity of AFB1 to human. Because of the specificities and high efficiencies of enzymes, more research is focused on enzymes that can transform aflatoxins directly.